The present invention concerns testing a container for leaks during an industrial fabrication process, and the device for implementing it.
Testing containers for leaks may be carried out using different detection methods.
A first known testing method is the method known as a “pressure variation test” which begins by establishing a determined excess pressure within the test container.
Next, the test container is plugged up, and the change in its internal pressure over time is measured. If there is a leak, the internal pressure decreases, and the measurement of this pressure decrease can be used to deduce the value of the leaks.
According to one variant of the method, a gas flow is injected into the test container so as to maintain the high internal pressure within the container. The gas flow value necessary to maintain this balance makes it possible to deduce the corresponding leak flows.
Another variant of the method begins by establishing a determined low pressure within the test container, then plugging up the container. In the event of a leak, the pressure increases and the measurement of this pressure increase is used to deduce the value of a leak.
These methods are simple to implement and inexpensive. However, the sensitivity of the measurement is limited, and depends on the particular conditions of the method's implementation.
Thus, the sensitivity depends on the volume of the test container, which is particularly harmful for test containers which have flexible walls and whose internal volume may vary over the course of the testing method.
Additionally, the time needed to conduct the measurement is too long for it to be integrated into a fast-paced industrial process, such as in the field of automobile manufacturing. Furthermore, the result of the measurement is sensitive to variations in the container's temperature.
The method for testing the leakproofness of test containers by detecting leaks using helium is also known.
To do so, an excess pressure of helium is established within the container. Next, it is detected whether helium is present within the ambient atmosphere surrounding the container using a sniffer connected to a leak sensor. The presence of helium is representative of a leak, and therefore of a leakproofness defect on the container.
The drawback of this method is that its usage is restricted to locating large leaks and that the sensitivity of the method is limited by the relatively high background noise of helium within the ambient atmosphere of the test room (the natural residual concentration of helium is generally above 5 ppm). Furthermore, the method is difficult to implement within an industrial process. Additionally, the use of helium is costly.
According to one variant embodiment of the helium detection method, the test container is placed within a sealed chamber connected both to a pumping room establishing an appropriate vacuum and to a helium leak sensor.
The internal space of the container is connected to a helium pressurization device, and leaks are sought out by detecting whether any helium is present within the internal atmosphere of the chamber, via the leak sensor.
This helium leak detection method is a reliable, reproducible, high-sensitivity test for carrying out a precise quantitative measurement, which may be incorporated into an industrial process. However, its implementation is restrictive.
First, the chamber itself must be made airtight so as to be able to support a vacuum. Next, the pumping devices must be suitable for the volume of the chamber to which they are connected. Thus, for high-volume test containers, large pumping units must be provided, which represents major investments and high maintenance fees.
Another drawback is that the sensitivity of the method is limited by the fact that helium has a tendency to very easily adsorb onto the surfaces of test containers, as well as onto the surfaces of the chamber receiving the container.
Consequently, removing pollution from the chambers after detecting containers that have a leak may be relatively slow and impede the industrial process.